A pension (/ˈpɛnʃən/; from Latin pensiō 'payment') is a fund into which amounts are paid regularly during an individual's working career, and from which periodic payments are made to support the person's retirement from work. A pension may be either a "defined benefit plan", where defined periodic payments are made in retirement and the contributions to the pension are adjusted to support these defined retirement payments, or a "defined contribution plan", under which defined amounts are paid in during working life, and the retirement payments are whatever can be afforded from the fund.

Pensions should not be confused with severance pay; the former is usually paid in regular amounts for life after retirement, while the latter is typically paid as a fixed amount after involuntary termination of employment before retirement.

The terms "retirement plan" and "superannuation" tend to refer to a pension granted upon retirement of the individual; the terminology varies between countries. Retirement plans may be set up by employers, insurance companies, the government, or other institutions such as employer associations or trade unions. Called retirement plans in the United States, they are commonly known as pension schemes in the United Kingdom and Ireland and superannuation plans (or super) in Australia and New Zealand.

A pension created by an employer for the benefit of an employee is commonly referred to as an occupational or employer pension. Labor unions, the government, or other organizations may also fund pensions. Occupational pensions are a form of deferred compensation, usually advantageous to employee and employer for tax reasons. Many pensions also contain an additional insurance aspect, since they often will pay benefits to survivors or disabled beneficiaries. Other vehicles (certain lottery payouts, for example, or an annuity) may provide a similar stream of payments. Individuals without access to employer-sponsored pensions sometimes use annuities to create a guaranteed income stream similar to a traditional pension.

The common use of the term pension is to describe the payments a person receives upon retirement, usually under predetermined legal or contractual terms. A recipient of a retirement pension is known as a pensioner or retiree.

A retirement plan is an arrangement to provide people with an income during retirement when they are no longer earning a steady income from employment. Often retirement plans require both the employer and employee to contribute money to a fund during their employment in order to receive defined benefits upon retirement. It is a tax deferred savings vehicle that allows for the tax-free accumulation of a fund for later use as retirement income. Funding can be provided in other ways, such as from labor unions, government agencies, or self-funded schemes. Pension plans are therefore a form of "deferred compensation". A SSAS is a type of employment-based Pension in the UK. The 401(k) is the iconic self-funded retirement plan that many Americans rely on for much of their retirement income; these sometimes include money from an employer, but are usually mostly or entirely funded by the individual using an elaborate scheme where money from the employee's paycheck is withheld, at their direction, to be contributed by their employer to the employee's plan. This money can be tax-deferred or not, depending on the exact nature of the plan.

Some countries also grant pensions to military veterans. Military pensions are overseen by the government; an example of a standing agency is the United States Department of Veterans Affairs. Ad hoc committees may also be formed to investigate specific tasks, such as the U.S. Commission on Veterans' Pensions (commonly known as the "Bradley Commission") in 1955–56. Pensions may extend past the death of the veteran himself, continuing to be paid to the widow.

In the U.S., retired military receive a military retirement pay, not called a "pension" as they can be recalled to active duty at any time. Military retirement pay is calculated on number of years on active duty, final pay grade and the retirement system in place when they entered service. Members awarded the Medal of Honor qualify for a separate stipend. Retirement pay for military members in the reserve and US National Guard is based on a point system.